Liquid crystal display devices have been attracting attentions as display devices that can provide features such as light weight, thin profile, and low power consumption. They are essential in everyday living and in businesses today for use in mobile devices, various monitors, large TVs, and the like. In particular, active matrix liquid crystal display devices using thin film transistors (TFT) as the pixel switching elements (driver elements) have significantly expanded their market share due to their favorable features such as a high contrast ratio and a fast response time. For such liquid crystal display devices, continuous research and development are being conducted for a better performance in image and display quality such as advanced multi-coloring and a higher resolution and for more versatile functions in response to expanded needs and further technological advancement.
A conventional liquid crystal display device disclosed (see Patent Document 1, for example) has a liquid crystal display panel configured to have two transparent substrates with liquid crystals sealed in between them. Of the two surfaces of the transparent substrates that are facing each other, one of the surfaces has an opposite electrode, color filters, an alignment film, and the like formed thereon, and the other surface has TFTs, pixel electrodes (display electrodes and common electrodes), an alignment film, and the like formed thereon. Such a liquid crystal display panel further includes a plurality of gate bus lines and a plurality of data bus lines crossing the gate bus lines formed thereon. An embodiment of this liquid crystal display panel includes black matrices, which are formed in parallel to the data bus lines, where the width of the data bus lines is set to 4 μm while the width of the black matrices is set to 8 μm. Substrates using copper or a copper alloy as the conductive film or the conductive lines are also disclosed (see Patent Documents 2 to 4, for example).